Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$237.66	11.712%	$265.4947	$265.49	$265.50	$265.50
Purchase #2	$143.94	8.182%	$155.7172	$155.72	$155.70	$155.70
Purchase #3	$116.81	6.482%	$124.3816	$124.38	$124.40	$124.40
Purchase #4	$112.28	13.675%	$127.6343	$127.63	$127.65	$127.60
Purchase #5	$93.47	10.388%	$103.1797	$103.18	$103.20	$103.20
Purchase #6	$106.97	5.276%	$112.6137	$112.61	$112.60	$112.60
Purchase #7	$119.78	4.319%	$124.9533	$124.95	$124.95	$125.00
7 purchase totals =	$930.91		$1,013.9745	$1,013.96	$1,014.00	$1,014.00